Actualize `Tty` and `TestTty` with Java classes

[JakeWharton]

With KT-67202 partially implemented, we might be able to eventually implement the JVM variant of 'mosaic-tty' fully in Java without a Kotlin stdlib dependency or Kotlin metadata.

Realistically we are blocked by at least KT-29882.

Also nice to have but not strictly needed is KT-15620.